What to do if there's a nuclear attack warning in the UK

First, what official advice exists

The UK's public advice is UKHSA's "go in, stay in, tune in". It's written for radiation emergencies, and UKHSA's examples are accidents, such as an incident at a nuclear power station or while radioactive material is being moved. The government's National Risk Register says a separate scenario for a nuclear attack on the UK "exists and is held at a higher classification", so there is no separate public UK leaflet for it.

Guidance written for nuclear weapons does exist elsewhere: the US government's Ready.gov page on nuclear explosions, Sweden's In case of crisis or war brochure and Finland's radiation guide all cover them. Their first step is the same as the UK's: get inside, stay inside, and listen for instructions. We use the UK advice first and the others only where the UK says nothing.

How a warning would reach you

GOV.UK says Emergency Alerts can be sent to mobile phones for any life-threatening emergency. A phone may make a loud siren-like sound for about 10 seconds, even on silent, and the alert includes a GOV.UK link or phone number. Alerts work on 4G and 5G networks, and you don't need to sign up. UKHSA also lists radio, television, the internet, social media and the police as ways advice will reach you.

Keep a battery or wind-up radio at home. If the power and phone networks are down, it may be the only way to hear what to do.

Step 1: Go in, straight away

• Get into the nearest solid building. Don't try to travel home. UKHSA says brick, stone or concrete buildings give the best protection.
• If you're with a pet outside, bring it in. Don't go out to look for a pet you can't see.
• Don't go out to collect children or relatives. UKHSA says they'll be asked to stay where they are.
• If there's a blast with no time to get inside, Ready.gov says to take cover behind anything that offers protection, or lie face down to protect bare skin, then get into a building as soon as the blast wave has passed. Sweden's brochure says lie down, preferably in a ditch or hollow.
• Ready.gov says that after a nuclear explosion you should have 10 minutes or more to find shelter before fallout arrives. Use that time to get into the best building you can reach.

Step 2: Pick the best room

• Middle of the building. UKHSA says stay as far from outside walls, doors and windows as you can.
• Basement, if you have one. Ready.gov says a basement or the centre of a large building is best, with as many walls between you and the outside as possible.
• A room without windows is better than one with windows (Sweden).
• In a block of flats, move away from outside walls and windows towards the core of the building. Underground car parks and stations can also give good shelter, according to Ready.gov and Sweden.

Why the middle? Ready.gov describes fallout as sand-like radioactive particles. UKHSA says being indoors with doors and windows shut protects you from breathing in material in the air and from radiation given off by material that has landed outside. The more walls, floors and distance between you and the outside, the less reaches you. Ready.gov sums this up as time, distance and shielding.

Step 3: Seal the room as well as you can

• Close outside doors and windows. Close trickle vents if you can.
• Turn off fans, air conditioning and anything that pulls in outside air (UKHSA). Ready.gov adds forced-air heating and fireplace dampers.
• Finland's guidance suggests sealing gaps with tape or cling film and switching off mechanical ventilation.

Step 4: If you were outside, clean up

UKHSA says your clothes, skin and hair may be contaminated if you were outside near the emergency.

1. Take off your outer layer of clothing carefully, without shaking it. UKHSA says this alone can remove around 90% of contamination. Put it in a bag and leave it away from people.
2. Shower or wash with soap or mild shampoo. Don't use hair conditioner: UKHSA says it can bind contamination to hair.
3. If you can't wash, Ready.gov says to wipe bare skin with a wet cloth or wipe, but not household cleaning wipes. Hand sanitiser doesn't help.
4. Wash pets with shampoo or soap and water, wearing gloves if you can.

Step 5: Stay in and tune in

• How long: UKHSA says you may need to stay indoors for one to two days, and longer if the release goes on. Ready.gov says at least 24 hours after a nuclear explosion, unless there's a fire, the building is collapsing, or officials say you can leave. Sweden says radiation levels drop sharply after a couple of days.
• Don't leave early. UKHSA says don't evacuate unless the authorities tell you to, because leaving can increase your exposure.
• Food and water: UKHSA says food and drink that were indoors, including tap water, are safe. Ready.gov says sealed containers that were outside are fine once wiped with a damp cloth; don't eat uncovered food or garden produce from outside until told it's safe.
• Iodine tablets: only if officials tell you to, and only tablets provided for this purpose. They protect the thyroid only. Don't use iodised salt.
• Listen to the radio and check GOV.UK when you can. Advice will change as officials learn more.

Myths you'll see online

• "I'll go and get the kids from school." UKHSA says don't: people in schools, nurseries and hospitals will be asked to stay where they are until it's safe to move.
• "The car will do as shelter." UKHSA says vehicles and tents don't give enough protection. Get into a building.
• "Take iodine tablets to be safe", or "give the children iodine regularly". Only take tablets provided for this purpose, and only when officials say. They protect the thyroid only, and timing matters.
• "Two weeks in a fallout room." That was the 1980 Protect and Survive plan. Current UKHSA advice is that you may need to stay in for one to two days, possibly longer, until officials say otherwise.
• "There'd be no warning, so why bother?" You may get one: Emergency Alerts reach 4G and 5G phones in the area. Getting inside fast and staying in is what the guidance says helps most.

What this advice can't promise

No guidance can promise safety. How much a shelter helps depends on how far away the emergency is, the building, the weather and how long you stay in. What official advice is clear on is the order: get inside fast, get to the middle, stay in, and follow instructions.

Get ready now, in calm time

• Decide your best shelter room at home, and think about work and school too.
• Keep 3 days of water (3 litres per person per day) and food that needs no cooking, as Be Ready suggests. You may need to stay in.
• Keep a battery or wind-up radio, a torch and a charged power bank.
• Agree with family that, in a warning, everyone shelters where they are and you'll meet up afterwards.

Related guides

• Radiation emergency in the UK: what official advice says (go in, stay in, tune in)
• UK Emergency Alerts: a calm guide
• Worried about war? How UK households can prepare — calmly
• The 72-hour emergency kit for UK households

We're an independent UK site, not the government. We check guides against official sources and link to them. In an emergency call 999.

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